We have to pay until we are 60 at the moment. The new rules of 30 years do not come into force for us oldies. I paid from 15 years to age 60. Made no difference how much I paid, it did not stop until I retired.
UK

At the moment national insurance contributions cease when we reach a certain age,until then you have to pay,i stopped paying when i reached 60,i think the age may be one or two years higher now,but you cannot decide when to stop,ring the national insurance helpline,they will have the answer, their number is---08459157006. By the way,its not just for your pension,its for the health service,dentist,and for any benefits you may claim.

You pay until you are old enough to receive the state pension when working.
If male and your expected state pension age is 65 (please remember this will change) and you have not reached 65 then you pay NIC on income.
NIC is not just the state pension - it is also the health service and benefits system.

You still need to pay until you reach the state retiring age because it's the law. It doesn't just pay for the pension, it pays for other social security as well, such as JSA if you lose your job - you don't get contribution-related JSA unless you've been paying right up to the point you became unemployed.

Previous answerers who say it contributes towards the NHS are wrong. It doesn't. NHS funding comes fully out of other taxes. I've seen the accounts of the National Insurance Fund and receipts of NI don't even fully cover the pension and contributory benefits - the fund has to get topped up out of other taxes. People have a misconception that it relates to the NHS because the NHS and NI started at the same time, and that might have been true in 1948, but it isn't now.